Stretch-shrink indicating and tension motor control apparatus



Jan. 11, 1966 R. c. STRANDBERG STRETCH-SHRINK INDICATING AND TENSION MOTOR CONTROL APPARATUS 2 Sheets-Sheet 1 Filed June 10, 1963 Variable Speed Drive-l3 To Control Mechanism INVENTOR ROBERT C.STRANDBERG BY WWW M ATTORNEY Jan. 11, 1966 R. c. STRANDBERG 3,229,175

STRETCH-SHRINK INDICATING AND TENSION MOTOR CONTROL APPARATUS Filed June 10, 1963 2 Sheets-Sheet 2 Decrease Increase lncr ease Comm 29 Common Motor Decrease H5 V. A C 34 To Terminals of Single Coil Meter l7 ROBERT C. STRANDBERG BY WW /.oe

ATTORNEY United States Patent 3,229,175 STRETCH-SHRINK INDICATING AND TENSION I MOTGR CONTROL APPARATUS Robert C. Strandberg, Greensboro, N.C., assiguor to Strandberg Engineering Laboratories, Inc., Greensboro, N.C., a corporation of North Carolina Filed June 10, 1963, Ser. No. 286,862 8 Claims. (Cl. 318-6) This invention relates to new and useful improvements in apparatus for detecting and indicating the percentage of stretch or shrinkage of a continuous web or strand moving through a processing machine. As such, the detecting and indicating apparatus of the invention is also adapted to actuate a suitable control mechanism for maintaining the stretch or shrinkage within predetermined limits.

As such the apparatus represents certain improvements in the apparatus disclosed in my copendingapplication Serial No. 161,082, filed December 21, 1961, now US. Patent No. 3,169,297, of which this application is a continuation-in-part.

My aforementioned copending application discloses a textile warp sizing and drying machine, known in the textile industry as a slasher, electrical means for producing a pair of voltages proportional to the speed of the textile warp at the entrance and exit ends of the slasher, an electrical logarithmic difference measuring device for producing a third voltage which is the logarithmic difference of the first pair of voltages, indicating means calibrated in terms of percentage shrink or stretch and responsive to the voltage output of the logarithmic difference measuring device, and automatic control means also responsive to the voltage output of the logarithmic difference measuring device for maintaining the stretch or shrinkage within predetermined limits.

In the warp sizing of yarn on a slasher, for example, the yarn is first immersed in a liquid starch bath and, after passing through squeeze rollers, it is dried, as for example by coming in contact with heater rollers or cylinders. Both yarn and fabric of natural or synthetic fiber content tend to stretch under tension to a greater extent when wet than when dry. Conversely, natural or machine introduced compressive shrinkage occurs when the material is being dried. The amount of stretch or shrinkage introduced into a warp or fabric by a textile machine is of importance. Slasher warp strength and weavability are influenced by stretch, and the amount of preshrinkage is highly significant in finishing textiles.

: The principal object of the invention is to conveniently and accurately detect and indicate the percentage of stretch or shrinkage in a continuously moving strand or web and, through an associated control mechanism, to hold the stretch or shrinkage within predetermined limits, without the necessity of periodically interrupting the movement of the strand or Web for stretch or shrinkage measuring purposes.

A particular object of the present invention is to provide an improved logarithmic difference measuring de vice in the environment as has been heretofore described.

It is another object of this invention to provide an improved automatic control mechanism for maintaining the stretch or shrinkage of a continuously moving strand or web within predetermined limits.

It is another object of the invention to provide an electrical logarithmic difference determining means for determining the logarithmic difference of the voltages produced by a pair of voltage generators, with transistor amplifiers interposed between the voltage sources and the logarithmic difference determining means to prevent voltage drop across the generators caused by current drain from the logarithmic difference measuring device, and

ice

thereby to produce an accurate logarithmic dilference measurement.

Other features and advantages of the invention will become apparent from the following description taken in conjunction with the accompanying drawings, wherein like characters of reference are used to designate like parts, and wherein: 1

FIGURE 1 is a diagrammatic illustration of a strand or web processing machine, showing the stretch-shrink indicating apparatus of the invention in association therewith;

FIGURE 2 is a wiring diagram of the apparatus;

FIGURE 3 is a diagrammatic illustration of the logarithm generating characteristics of the diode-resistance combination used in the apparatus;

FIGURE 4 is a wiring diagram of the automatic control apparatus of this invention for maintaining the percentage shrink or stretch within predetermined limits; and

FIGURE 5 is a wiring diagram of the improved logarithmic difference measuring circuit of this invention.

The apparatus disclosed in FIGURES 1 through 3 was disclosed in my aforementioned pending application Serial No. 161,082. Description of the apparatus shown in FIGURES 1 through 3 is made here for purpose of background information and for showing the environment in which the improved apparatus shown in FIGURES 4 and 5 is used.

Referring now to the accompanying drawings in detail, particularly to FIGURE 1, the strand or web being processed is indicated by the reference numeral 10 and is shown as moving continuously in the direction of the arrows, first passing through a Wetting agent or a sizing solution, as for example, a liquid starch bath 11 and then through squeeze rolls 12 driven by a variable speed drive of a suitable type indicated generally by the reference numeral 13. A variable speed drive, in the ordinary sense, consists of some prime mover, either an electric motor or a shaft common to some other part of the system, and a means for changing its speed. If the variable speed drive utilizes a D.-C. motor, for example, a reversing switch would be connected to the terminals of a small reversible motor, the shaft of which would operate a rheostat connected in circuit with the motor armature or field winding. As the reversible motor shaft position is changed by the operation of the reversing switch the speed of the drive is changed. If the variable speed drive utilizes a common shaft as a prime mover, a similar reversible motor would be attached to an integral part of the drive to adjust the position of a belt on a set of variable-pitch pulleys.

The electric motor type drive is often referred to as a variable speed D.-C. drive. The common shaft type drive is often referred to as a Reeves or PIV drive. Both of these drives are conventional and no claim is made in connection with their operation.

From the rolls 12 the strand or web 10 passes around a plurality of suitably heated cylinders or rollers 14 where it is subjected to drying, and eventually passes over a roll 15 to a loom beam or other take-up 16.

The stretch-shrink apparatus utilizes two direct current generators G and G the former of which is driven by the variable speed drive 13 in synchronizationwith the rolls 12, while the latter is driven from the roll 15. The drive arrangement is such that in the absence of stretch and shrinkage in the strand or web 10, the movement of the strand or web rotates arm atures of the generators G and G at the same speed. However, if the Web is stretched during its passage over the drying rolls 14 the generator G is driven faster than the generator G Conversely, if the web is shrunk the generator G is driven at a slower speed than the generator G The wherein X is the percentage or stretch expressedeas a pofsitivernumbe'ror the percentage of shrinkage expressed ti e negative niiirlben'ands and S are, respectively, the Sfid 6f theig'iieratdrs Gi Etlld G2. N

In terms of outputvoltages V and V of the respective generators G and G the equation becoines V2 V1 l X or simply V1 1 where 1 a number greater, than 1 in the instance of stretch or lessthanl'in the instance of shrinkage. I

The generators'G and G areconnected to a suitable, single coil meter 17 which is arranged tojmeasu're the ditterence in the voltageoutput of the two generators and the meter polarity is made to accommodate either stretch or sh inka H I Asindicatedin EIGIJTRE 2, the generators G and G are c gnnected to the meter 17 in circuit with two silicon (liQdes D and D and a resis'tance 18;, and thevolta'ge developed vacross the diode D is a logarithmic ttunction of the voltage output V of the generator G which is driven at the speed S Similarly, thevolta-ge developed across the, diode D is alogari-thmic tunctionot the volt age cytput V of the generator G which is driven at esr t t -The logarithm generating characteristic of the 'diodere ista ce combination is exhibited in the region of very low current magnitudes, as illustrated in FIGURE 3., As thecurrent through the diode/D increases, the voltage drop ,V across thediode, increases only slightly in relation to large, increases, in the; voltage source V.

Referring again to the aforementioned equation the meter 17 may be calibrated in terms of positive pert sh endn s ti cpp c t shr n nd the n mber 1- nt c quatio m be .dr rr T he voltage V applied to the meter is proportional to log V log V or log ,Asfuiiabie set-point controller .is shown, generallyby ther fernce-inumelnal 19 in FIGURE The set-point controller, be described 'inmore detail with respect tottheernbodirr ient shown .in FIGURE 4. Its purpose is to vprovide means whereby an operator can set the predetermined limits within which the automatic control mechanism maintains stretch or shrinkage. The setpoint controller is connected across the meter Hand in circuit with a suitable speed control reversing switch 29 for o periating the variable speed drive 13 so that the stretch or shrinkage of. the web may be automatically maintained within predetermined limits.

purpose of thecontrol device shown in FIGURE is to automatically actuate a reversible control motor 30 as shown, the shaft position of which will determine the speed of -a conventional variable speed drive 13. The device utilizes a photoelectric meter relay 31 to sense a departure from the desired stretch or percentage ditterence between input and output speed. The photocells actuate relays to cause a control motor, either through a separate reversing switch or directly, to either increase or decrease the input speed depending upon whether the percentage stretch is higher or lower, respectively, than the desired aniount. A D;-C. voltage tromthe terminals of the single-coil meter 17, already described, is applied across potentiometer 32. A portion of this voltage is applied to the moving coil 33 of a three-position photoelectric meter relay. The meter relay consists oftwo light sources 34, 34', light shading pointer 35 mechanically attaehed tothe moving coil '33, and two closely spaced photoelectric cells 36 and 37. s

The photoelectric cell 36 in series with resistor 38 and the photoelectric cell 37 in series with a resistor 39 are connected inparallelbranches across the A.-C. lincZQ. A pair of gas control tubes 40 and in parallel branches across the A.-C. line 29 are controlled respectively by the photoelectric cells 36- and 37.

Gas, control tube 40 includes acontrol "grid 41, a cathode 42 and an anode 43. The control grid 41 is connected between the resistor 38 and the photoelectric cell 36;; the cathode 42 is connectedto one of the A".-1C. lines; and the -anodej43 is connected in s'eries with the energizing coil of a plate relay 44 tov the other A.-C. line.

Similarly, gas control tube 44 includesa contact grid 46, a cathode 47 and an anode ls The controljgrid 46 is connected between the resistor 39 and thje photo electric cell 37; the cathode 47 is connected, to one of the A,-C. lines; :and the anode 48 is connected in series with the energizing coil of a plate relay 49 to the other A-e -l cv, p v

Resistor-capacitor networks 51and50g and 5 3 and 52 are connectecl across the plate relay coils 5 4 and 55 respectively, for the purpose of providing filteringof the pulsating D.-C. current which 'is rectified and passed by the gas control tubes 40 and 45.

v The plate control relays 44 and l9factuate reversing m c an s o t e ontro mot r 3 l e e y 44 an 49 haye a set of movable contacts'56, 57 and 60,161 respectively, and a set of fixed contacts 5'8,'59'and 62, 63 p c e y r, v v Q The lower movablecontacm 5'7 and -j;61 of the respective relays are connected to the common lea'd of the control motor 30. The lower fixed contact 59 of relay 4,4 is connected tothe decrease terminal of control motor 30, and; the lower fixed contact 63 of th'e relay 49 is connected to the increase terminal of the control motor 30. v, l t

v Actuation of either lower movable "contacts 5.7 or '61 to engage its corresponding "lower fixed-contact 59 or63 causes the control motor to reverse its direction of movement for the purpose of decre'asingor increasing the speed ofjthe variable speed drive unit 13., v V

The uppermo'vab'le contacts 56 and of the relays44 and 49 respectively are connected'to one side of the A-.-C.- line. Thefixed contact 58 is connected in series with a resistor 64 and neon light 65, to the other sidefof the A.'-C. line. Similarly, the fixed contact" 62 is connected in serieswith resistors 66 and 67 to the other side of the A.-C. line.

The circuitsjshown in FIGURE 4 which have been heretofore described will be better understood by the following explanation oftheir function:

Thepotentiometer 321is calibrated in terms of Percent Stretchj Percent Shrinkage," or both corresponding to the value'of voltage from 'theterminalsof the meter 17 which will cause the D.-C. voltage selected by the potentiometer 32 to be such that the light shading 'p'oint er 35 of thephotoelectricmeter relay will'be-positioned photoelectric cells 36 and 37;

- When the r'rie'as'ufed percentage stretch increases from the desired value set on the potentiometer 32 the light shading pointer 35 will move upward and shade the light from the upper photocell 37. Similarly, when the measured percentage stretch decreases from the desired value set on the potentiometer 32 the light shading pointer will move downward and shade the light from the lower photoelectric cell 36. Mechanical stops (not shown) are employed so that the pointer cannot travel beyond the completely shaded positions of each photoelectric cell.

The lower photoelectric cell 36 is connected in series with resistor 38 across the A.-C. line. When the cell is illuminated its resistance is low and the A.-C. voltage developed across it is low. When the cell is shaded, as would be caused by a decrease in the percentage stretch, the cell resistance is high and the A.-C. voltage developed across it is high.

Since the A.-C. voltage developed across the photoelectric cell 36 is applied from the control grid 41 to the cathode 42 of a gas control tube 40 the tube will conduct when its grid 41 and anode 43 are positive with respect to its cathode 42.

Since a plate relay 44 is connected in the anode circuit of the gas control tube 40 it is energized by a decrease in the percentage stretch below the value set on the potentiometer 32. The energizing current is pulsating D.-C. rectified andpassed by the tube 40.

As described, when the upper photoelectric cell 37 is shaded, as caused by an increase in the percentage stretch, the grid to cathode voltage applied to a second gas control tube 45 is increased sufficiently to cause conduction in its anode circuit through plate relay 49.

When the percentage stretch is equal to the value set on the potentiometer 32, the low-stretch relay 44 and the high-stretch relay 49 are both de-energized. When the percentage stretch is low, the low-stretch relay 44 is energized and the high-stretch relay 49 is de-energized. When the percentage stretch is high, the high-stretch relay 49 is energized and the low-stretch relay 44 is de-energized.

The upper set of contacts associated with each relay serves to operate signal lights to show when the control is measuring a deviation from the pre-set value set on the potentiometer 32 and in which direction the control is acting to correct it. Ordinary neon indicator lamps 65 and 67 are employed with current limiting resistors 64 and 66.

The lower set of contacts associated with each relay close the control motor 30 circuit from common to increase or decrease, depending upon the direction of deviation in the percentage stretch. When the percentage stretch is determined to be low with respect to the set point on the potentiometer 32, the control motor shaft is caused to rotate to a position which will reduce the speed of the variable speed drive 13 to a value which will permit the percentage stretch to be equal the amount set. Similarly, when the percentage stretch is high, the control motor causes the speed of the variable speed drive 13 to be increased until the percentage stretch is equal the amount set.

The shaft connection between the control motor 30 and the variable speed drive 13 has not been shown. It is believed that the explanation heretofore given is sufficient for an understanding of the control system so that a person familiar with conventional variable speed drives can adapt the control system of FIGURE 4 for use with any one of several types of conventional variable speed drives, several of which have been mentioned heretofore.

The circuit shown in FIGURE 5 differs from the original one shown in FIGURE 2 in that transistor amplifiers have been inserted between the generators 61 and 62 and the logarithm generating device.

Difficulty has been encountered with variations in voltage output from the generators when used in the circuit shown in FIGURE 2. The variations in voltage were due to variations in voltage drop across the generator brushes. Since the measurement involves subtracting one relatively large number from another, it is most important that the generator output voltages be exactly related to speed.

The terminal voltage from D.-C. generators is basically related to speed, if no current is flowing through the brushes. The transistor amplifiers serve to block the flow of current and produce an output which is exactly related to the generated voltages.

The use of the transistor amplifiers eliminated long and short term drift due to voltage drop across the brushes. Since no current is allowed to flow through the brushes the terminal voltage is equal to the generated voltage.

Referring to FIGURE 5, the generated voltages from generators G and G are applied from the bases of transistors 70 and 71 to acommon connection 72 between the two generators. Proportional currents are caused to flow from the positive terminal +E of a conventional D.-C. power source through common resistor 74 and separate emitter circuit resistors 75 and 76, through the transistors from emitter to collector, and through separate collector load resistors 77 and 78 to the negative terminal E of the D.-C. power source.

The D.-C. voltages produced across resistors 77 and "1'8 are the proportional to the generator voltages and are applied to the meter 17, diodes D and D and resistor 18 in the same manner as described for the circuit shown in FIGURE 2.

While in the foregoing there has been described and shown the preferred embodiment of the invention, various modifications may become apparent to those skilled in the art to which the invention relates. Accordingly, it is not desired to limit the invention to this disclosure and various modifications and equivalents may be resorted to, falling within the spirit and scope of the invention as claimed.

' What is claimed as new is:

1. In automatic electric stretch-shrink indicating and control apparatus for continuously running webs and the like, the combination of first and second voltage generators disposed at points spaced longitudinally of the running movement of the web, the voltage output of said generators being directly proportional to their respective speeds, first and second logarithmic function producing means connected respectively in circuit with said first and second voltage generators for converting the output voltages of said voltage generators to logarithmic functions thereof, a meter in circuit with said first and second logarithmic function producing means for measuring the difference in their voltage output, a pair of current limiting amplifier means connected respectively in the circuit between said first voltage generator and said first logarithmic function producing means and in the circuit between said second voltage generator and said second logarithmic function producing means, and speed control means responsive to variations in the difference voltage output of said first and second logarithmic functions producing means for maintaining the stretch-shrink factor of the web within predetermined limits.

2. The device as defined in claim 1 wherein said first and second logarithmic function producing means comprise first and second diodes in circuit with the respective first and second generators and said meter, and a common resistance between said generators and said diodes, the voltage developed across each diode being a logarithmic function of the voltage output of its respective generator.

3. The device as defined in claim 2 wherein each of said diodes comprises a silicon diode.

4. The device as defined in claim 1 wherein said pair 2f current limiting amplifier means are transistor ampliers.

5. In automatic electric stretch-shrink indicating and control apparatus for continuously running webs and the like, the combinations of first and second voltage generators disposed at points spaced longitudinally of the running length of the web and adapted to be driven by the running movement of the web, the voltage output of said generators being directly proportional to their respective speeds, first and second logarithmic function producing means connected respectively in circuit with said first and second voltage generators for converting the output voltages of said voltage generators to logarithmic functions thereof, a meter in circuit with said first and second logarithmic function producing means for measuring the difference in their voltage output, a pair of current limiting amplifier means connected respectively in the circuit between said first voltage generator and said first logarithmic function producing means and in the circuit between said second voltage generator and said second logarithmic function producing means, together with a variable speed drive for imparting running movement to said Web, and automatic control means controlling said variable speed drive and responsive to variations in the-difference in voltage output of said first and secondlogarithmic functions producing means for maintaining the stretch-shrink factor of the web Within predetermined limits.

6. The combination as defined in claim wherein said automatic control means comprises a reversible control motor for setting the speed of said variable speed drive,

reversing means in circuit connection with said control motor, a pair of photoelectric devices in circuit connection with said reversing means for controlling said reversing means to effect reversal of direction of movement of said control motor, light varying means controlling the. light impinging on said photoelectric devices in response to variations in the vdiiference in voltage output of said first and second logarithmic function producing means.

7. The combination as defined in claim 6 wherein said light varying means comprises a photoelectric meter relay consisting of aseparate light source for each photoelectric device, a moving coil, a'shading vane mechanicallyconnected torsaid moving coil so as to move alternately between one or the other photoelectric device and its respective light source in response to voltage variations in the difference in voltage output of said first and second logarithmic function producing means, and an adjustable 8- potentiometer in circuit with said moving coil and connected across said single coil meter whereby the shading vane may be centered between its alternate extreme positions of movement at a predetermined value of the difference in voltage output of said first and second logarithmic function producing means.

8. The apparatus as set forth in claim 6 wherein said reversing means comprises a pair of reversing relays in circuit connection with said control motor, and a pair of gas control tubes in circuit with said reversing relays respectively so that when said gas control tubes are conductive said reversing relays are energized, said. gas control tubes also being each in circuit with a respective one of said photoelectric devices and under control thereof.

References Cited by the Examiner UNITED STATES PATENTS 2,244,369 6/1941 Martin 235- X 2,486,068 10/1949 Shishini et al. 235-195 X 2,586,076 2/1952 Nichols 318-6 2,747,148 5/ 1956 Peeples 318-6 2,777,964 1/1957 Di Mino 318-6 X 2,875,388 2/1959 Scheu 318-7 2,885,763 5/1959 Schreiner 26-186 3,035,193 5/1962 Ethier 318-6 X 3,114,850 12/1963 Hansen 318-6 X 3,156,397 11/1964 Davies 318-6 X 3,169,297 2/ 1965 Strandberg 28-28 FOREIGN PATENTS 815,063 10/1951 Germany.

438,690 11/1935 Great Britain.

875,473 8/1961 Great Britain.

OTHER REFERENCES Maynall: Electronic Analogue Computing, Electronic Engineering, July 1947, page 214.

German application E9220, March 1956.

JOHN F, COUCH, Primary Examiner. R ERT M CKE Ex mine T. LYNCH, Assistant Examiner. 

1. IN AUTOMATIC ELECTRIC STRETCH-SHRINK INDICATING AND CONTROL APPARATUS FOR CONTINUOUSLY RUNNING WEBS AND THE LIKE, THE COMBINATION OF FIRST AND SECOND VOLTAGE GENERATORS DISPOSED AT POINTS SPACED LONGITUDINALLY OF THE RUNNING MOVEMENT OF THE WEB, THE VOLTAGE OUTPUT OF SAID GENERATORS BEING DIRECTLY PROPORTIONAL TO THEIR RESPECTIVE SPEEDS, FIRST AND SECOND LOGARITHMIC FUNCTION PRODUCING MEANS CONNECTED RESPECTIVELY IN CIRCUIT WITH SAID FIRST AND SECOND VOLTAGE GENERATORS FOR CONVERTING THE OUTPUT VOLTAGES OF SAID VOLTAGE GENERATORS TO LOGARITHMIC FUNCTIONS THEREOF, A METER IN CIRCUIT WITH SAID FIRST SECOND LOGARITHMIC FUNCTION PRODUCING MEANS FOR MEASURING THE DIFFERENCE IN THEIR VOLTAGE OUTPUT, A PAIR OF CURRENT LIMITING AMPLIFIER MEANS CONNECTED RESPECTIVELY IN THE CIRCUIT BETWEEN SAID FIRST VOLTAGE GENERATOR AND SAID FIRST LOGARITHMIC FUNCTION PRODUCING MEANS AND IN THE CIRCUIT BETWEEN SAID SECOND VOLTAGE GENERATOR AND SAID SECOND LOGARITHMIC FUNCTION PRODUCING MEANS, AND SPEED CONTROL MEANS RESPONSIVE TO VARIATIONS IN THE DIFFERENCE VOLTAGE OUTPUT OF SAID FIRST AND SECOND LOGARITHMIC FUNCTIONS PRODUCING MEANS FOR MAINTAINING THE STRETCH-SHRINK FACTOR OF THE WEB WITHIN PREDETERMINED LIMITS. 